The disclosure relates to a hydraulic axle.
In the context of this application, a hydraulic axle is to be understood to mean a hydraulic actuator, for example a hydraulic cylinder, and the hydraulic or electro-hydraulic control arrangement or circuit that charges the actuator with fluid. Such hydraulic axles are compact and powerful high-performance drives. They can be used for numerous industrial automation applications, for example in presses, plastics machines, bending machines and so forth. In particular, such drives are designed for realizing at least two movement profiles, specifically a fast transfer movement—hereinafter referred to as rapid-traverse stroke or rapid-traverse movement—and a force-imparting working movement—hereinafter referred to as power stroke, working movement or pressing stroke.
A known hydraulic axle is presented in the applicant's application DE 10 2009 043 034. A main cylinder, a rapid-traverse stroke cylinder and a hydraulic machine which can be reversed in terms of its direction of rotation are interconnected in a preloaded hydraulic system. By means of valves, the interconnection of the components can be varied such that one of several hydromechanical transmission ratios predefined for example by means of piston surfaces is selected. In this way, the said rapid-traverse movements or working movements can be performed in an efficient manner.
Furthermore, the applicant's DE 10 2012 020 581 discloses a hydraulic axle with a multi-surface cylinder. The latter has one deployment surface and two retraction surfaces. In the rapid-traverse stroke, the deployment surface and the first retraction surface are fluidically connected to one another by means of a regeneration valve and, together, have a pressure medium connection to the second retraction surface via a hydraulic pump. During the rapid-traverse deployment stroke of a piston of the multi-surface cylinder, for example, it is thus possible for the deployment surface and the first retraction surface to be connected to a high-pressure side of the hydraulic pump. The hydraulic pump then delivers pressure medium from the second retraction surface to the deployment surface and to the first retraction surface. A resulting exertion of pressure on the deployment surface and on the first retraction surface has the effect that numerous seals are subjected to a high pressure. In particular at seals of a chamber that is delimited by the outer, second retraction surface, the exertion of pressure leads to high friction resistances, such that in particular in the rapid-traverse stroke, high pressures are required to move the piston.